Electric Submersible Pump (ESP) systems are used in a variety of well applications. ESP systems may comprise centrifugal pumps having a plurality of stages with each stage employing a diffuser and an impeller. In oil wells producing substantial amounts of sand, the lifetime of the centrifugal pump may be shortened due to excessive wear. The sand tends to wear on the pumping system components and increases clearances in the case of radial wear. This type of wear can lead to a decrease in the head flow and an increased horsepower demand, thus affecting pump performance. The abrasive sand also can cause holes to develop in diffuser walls and can lead to erosion of pump passages.
Erosive wear often occurs at points where flow discontinuities exist and also in void areas of the diffuser and impeller where sand can get entrapped and circulated. During operation of the ESP system, sand can get trapped between the impeller lower shroud and the bottom surface of the diffuser cup. In spite of the large clearance in this area, the spinning action of the impeller causes a wave action at the point of unison of the bottom inside surface of the diffuser and the inside side wall. Due to the tangential velocity of the cavity fluid discharged by the impeller, the swirling of the sand at the point of unison between the bottom inside surface and the inside side wall of the diffuser causes an erosive action at this junction and eventually may cut through the diffuser wall. Severe erosion of the upper shroud in radial flow impellers can lead to separation of the upper shroud from the impeller hub. Sand particles also can settle between the outer rim of the impeller bottom shroud and the diffuser inner wall and become trapped, thus moving around until they are reduced in size or cut through the wall of the diffuser. However, attempts to reduce the velocity of the cavity fluid tend to create friction or drag, and the degree of such drag increases exponentially with radius, e.g. the radius of the impeller.